The present invention relates to improvements in semi-frozen, frozen food product or beverage refrigeration machines, and more specifically, relates to improved structures for improving the quality, consistency, and efficiency of operation while improving product yields and ease in cleaning of machinery utilized in the manufacture and dispensing of semi-frozen, frozen food products or beverages.
An important structure in a softserve product refrigeration machine is the dispensing door construction, which usually also carries with it the product dispensing valve mechanism utilized for removing product from the freezing cylinder (evaporator). An ideal door would be one which minimizes condensation so that it does not have to be continuously attended to by an attendant; one that provides an excellent seal for the freezing cylinder when the door is closed; is designed so that the seal between the door and the freezing cylinder does not create an obstruction which catches the softserve product, or inhibits proper drainage of product/cleaning and/or sanitizing fluids therefrom when the freezing cylinder is being cleaned. Many designs have utilized a flat gasket between the door and freezer, such as the Clifford patent (U.S. Pat. No. 3,050,960, issued on Aug. 28, 1962), which construction requires a high pressure being exerted to effect a proper seal. Other designs have utilized an O-ring captured inside the freezing cylinder and projecting or protruding from the interior surface of the freezing cylinder. While an O-ring eliminates the need for high forces, it obstructs the proper drainage of product from the freezing cylinder. In essence, the O-ring design requires that the product exit port be raised above the bottom edge of the freezing cylinder by an amount equal to the width of the O-ring seal. In this manner, it is difficult to provide proper drainage of product or cleaning and/or sanitizing fluids when cleaning both the door and the freezing cylinder. It should be mentioned that U.S. Pat. No. 2,916,044, issued on Dec. 8, 1959, does illustrate a cover and serving valve for freezers utilizing an insulation which is primarily for inhibiting condensation due to the capturing of the retard (or baffle) in the cover.
Another important aspect of a properly designed softserve product refrigeration machine is the dispensing valve mechanism. While valve mechanisms have varied, it is absolutely essential that the mechanism be easy to clean. That is, the valve mechanism must have no physical internals which allow for food product retention such that it can be easily cleaned by flushing with sanitizers. Valve designs which use a plunger with O-rings have small crevices between the moving parts where food product becomes lodged and is difficult to remove in the cleaning process. These designs, moreover, allow leakage of food product past the O-ring and this leakage of food product makes it incapable of effective cleaning in a clean-in-place process. Moreover, this kind of design must be lubricated, which usually requires disassembly. Another desirable feature of an ideal dispensing valve is that all product in the dispensing spout should be forced from the valve leaving no residual product to later melt and dip.
In order that the reader may better understand the nuances of the softserve refrigeration and freezing process, the following material is tendered, and directed towards various ones of the copending applications set forth above.
Normally, semi-frozen, frozen confection food product or beverage (hereinafter xe2x80x9csoftserve productxe2x80x9d) is drawn from a freezing cylinder or chamber (evaporator) at intermittent times. However, the product must be in a proper state for serving when it is needed. Conventionally, to maintain product temperature and/or viscosity at an ideal state, the main refrigeration system is required to run quite frequently. Moreover, dependent upon the draw of the softserve product, additional quantities of product mix, usually kept at a refrigeration temperature below 41 degrees Fahrenheit to prevent spoilage, requires an increase draw of such mix, proper aeration or xe2x80x9coverrunxe2x80x9d, which of course, creates further cycling of the main refrigeration system.
Numerous attempts have been made to reduce this refrigeration system recycling so as to increase the efficiency of the system. For example, in U.S. Pat. No. 5,386,709 (issued on Feb. 7, 1995), methods and apparatus are disclosed for incorporating thermal storage and other low temperature reservoirs with a secondary or retrofitable refrigerant circuit to increase the thermal operating capacity and efficiency by subcooling refrigerant condensate with subcoolers. However, auxiliary power equipment is required, once again lowering the overall system efficiency making it undesirable for softserve product dispensing refrigeration machines. In other systems, such as in U.S. Pat. No. 4,643,583 (issued on Feb. 17, 1987), a eutectic liquid is introduced into a space intermediate an inner metal vessel and an outer case. The purpose of the provision of a eutectic liquid is purportedly to maintain the vessel at a nearly constant temperature so as to ensure whisking (or commonly referred to as scraping) of the ice cream mixture within the cold storage container. But this system also requires a second refrigeration system in order to maintain the container at the whisking temperature.
During the transition from active freezing of the product to the idle state of the refrigeration system, the temperature of the evaporator must be raised to prevent xe2x80x9cstickingxe2x80x9d of the scraping or beater blades upon subsequent restarts. To accomplish this, the evaporation temperature should be preferably raised to within a few degrees of the product temperature. In this manner, xe2x80x9cstickingxe2x80x9d of the scrapers on the next restart does not occur. This is accomplished in the novel softserve apparatus by a novel method and means without necessitating a second refrigeration system.
It is well-known that it is essential for consistency of softserve product that an amount of gaseous matter such as air should be incorporated into the liquid ice cream mix at the time of freezing. xe2x80x9cOverrunxe2x80x9d, which is defined as a percentage, may be determined in a number of ways, one such way is:       (                            W          L                          W          P                    -      1        )    xc3x97  100
WL=Weight of volume (test) of raw liquid mix
WP=Weight of an equal volume of product (including air)
Overrun is accomplished either with a feed tube and air orifice in a gravity style freezer, such as illustrated in U.S. Pat. No. 5,706,720 (issued on Jan. 13, 1998) or a pump in a pressurized freezer. The feed tube method does not provide accurate control of overrun because the liquid fill rate is dependent upon the mix level in the hopper and the air flow rate is affected by xe2x80x9cbarrelxe2x80x9d pressure. Thus, when product is being dispensed from the freezer, a pressure drop is sensed in the barrel (the feed tube or conduit which supplies applying mix and air to the freezer unit) changing the overrun percentage. Thus, with this type of apparatus, at best, a limited overrun range is provided and it is difficult to control the percentage (%) of overrun.
In a pressurized freezer, a pump is employed which provides somewhat improved accuracy allowing for a greater range of overrun but requires physical component change to vary the overrun settings. Moreover, the pump also adds a degree of complexity to the freezer operation because of the number of components that must be cleaned, lubricated and reassembled. Once more, the control of overrun by the pump is effected by the draw rate of the softserve product. Since the pump is a positive displacement device for the liquid portion and a pressure sensitive device for the air portion, while the liquid mix flow rate is not affected by changes in barrel pressure, which can vary with the draw rate, the air flow rate, being pressure sensitive, will vary as the barrel pressure changes. Such a system is shown in U.S. Pat. No. 4,457,876 (issued on Jul. 3, 1984). Once again, it would be desirable to provide a system which would allow control of overrun by an accurate setting of the overrun. Moreover, the system provided should be easily cleaned, preferably without removing or disassembling the system such as necessary with a pump system.
Once the mix and proper air mixture has been fed into the freezer, it is vital that the mix be moved or beaten so that a continuous folding or blending of the nearly frozen mixture occurs in the freezing cylinder, and that the material as it freezes in the freezing cylinder is whisked or scraped off and dropped back into the mix for further blending and movement within the cylinder. Most beater designs have involved a framework of stainless steel bars and castings. In fabrication, these designs required a large amount of welding or brazing to complete the manufacture. Moreover, welding oftentimes proves to be less sanitary than desired and the brazing operation also lacked compatibility with highly acidic mixes. While there have been many designs recommended for beater construction (see Re. 32,159 of May 27, 1986, which utilizes insertable blades), and the design illustrated in U.S. Pat. No. 512,002 (issued on Jan. 2, 1894), all of these designs require massive constructions and are difficult to fabricate in order to arrive at a strength sufficient to be able to properly fold or beat the softserve product. What is required in a properly constructed beater assembly is not only great strength (because the softserve product, such as a frozen confection e.g., softserve ice cream, is very stiff and offers high resistance to the rotation of the beater assembly or dasher) but also something that is easy to construct, will give better blending of the mix within the freezing chamber, and therefore give a consistently higher quality product at a higher throughput.
In an ideal softserve product refrigeration machine, it is desirable to provide a simple method for sensing the level of mix so that the equipment operator may be forewarned when the mix is almost depleted, as well as to inform him periodically as to how much mix is left in the product feed conduit to the freezing cylinder. Numerous prior art systems have been employed for level and/or amount sensing. For example, in U.S. Pat. No. 4,386,503 (issued on Jun. 7, 1983), pressure differences are used to regulate the supply of liquid P2S5 which allows for measurement of the liquid level in the device with respective pressure differences being utilized for regulating the supply of the liquid P2S5 to the cooling device. In this manner, a predetermined liquid level may be maintained. Moreover, patents such as U.S. Pat. No. 3,646,774 (issued on Mar. 7, 1972) utilize pressure sensitive switches for measuring material levels, while patents such as U.S. Pat. No. 4,417,610 (issued on Nov. 29, 1983) utilize some kind of pressure sensor located up stream of an outlet valve for effectively adjusting a length of the opening time interval as a function of a variation of an average medium pressure between consecutive operations of operating cycles of the outlet valve arrangement.
Conventionally, softserve machines require daily cleaning and/or sanitizing to insure that undesired bacteria and the like are eliminated. Because of the intricate parts of such machines, traditionally the machines must be disassembled and each part that contacts food thoroughly decontaminated and cleaned. The machine is then reassembled. This process can require trained personnel and personal attention several hours a day. Moreover, this procedure usually occurs after normal operation hours requiring overtime or additional personnel. What has long been desired, is a machine design which allows for xe2x80x9cclean-in-placexe2x80x9d and employs a method of cleaning that is reliable and safe, is quick and which does not require disassembly and reassembly of the machine while insuring cleanliness of the machine. That is accomplished by a softserve product refrigeration machine disclosed herein. As will be seen, special machine construction allows for complete xe2x80x9cclean-in-placexe2x80x9d operation without disassembly of the machine for cleaning.
A principal limitation of existing softserve product refrigeration machines is that they are setup xe2x80x9ctunedxe2x80x9d to run well under a typical set of environmental variables. Examples of these variables would be temperature, humidity, mix composition, power (electrical) quality, and the manner that the operator uses the machine. Whenever the machine is operated outside of the median point of these parameters (and others) the product quality suffers, in most cases not to a large degree but suffers nonetheless. In general the systems in use today must live with this loss. What is preferable, and what is accomplished advantageously with the softserve machine described herein, is a fully integrated system of mechanical and refrigeration hardware, electronic hardware, and software. This full integration allows each portion of the machine to perform functions that are best suited to that particular technique.
In view of the above, a principal advantage of the present invention is the novel dispensing door assembly for the freezing chamber or cylinder. To this end the assembly ensures tight closing of the freezing cylinder at the end thereof from which product egresses the freezing cylinder, and which, in conjunction with the novel cover design and interlocking dispensing valve design, ensures good locking action of and closing off of the freezing cylinder. Moreover, the advantage of the special cover design for the door not only ensures interlocking with the product dispenser to prevent inadvertent displacement of the door, but also inhibits condensation, which normally would occur because of the high temperature difference between the freezing cylinder and the atmosphere outside of the dispensing valve and door. To achieve these advantages, the freezing chamber includes a tube having a rim at one end thereof, the door assembly including a door, including alignment lugs on one of the door and the rim, and apertures, intended for reception of the lugs on the other of said door and rim, to ensure proper alignment of the door with the rim. An annular projection on one of the door and rim and an annular receptacle on the other of the door and rim, align when the door is in position in mating engagement with the rim. The inclusion of a Z-shaped (in cross section) seal fittable in the receptacle (with a depending radial extending lip) serves to receive the annular projection, the cup providing a radial seal and the lip providing an axial seal therewith. The cover member has an exterior and interior portion, the interior portion having a door engagement portion to cause pressing engagement between the door and the rim. A locking collar on the exterior portion of the cover provides locking engagement with the rim of the freezing cylinder, the major portion of the interior portion of the cover being spaced from the door to form an insulating air space to inhibit condensation.
Yet another advantage of the present machine structure is the ability to maintain the cleanliness of both the freezing cylinder and the associated door, cover and dispensing valve. To this end, a passageway in the door receives product from the freezing cylinder for communication with a product outlet from the door. A receptacle for insertion into the door is in a path aligned with the product outlet and a product dispensing valve is disposed in the receptacle. An aperture in the cover is aligned with the receptacle and engageable thereby, in conjunction with the valve, to retain and lock the cover to the door. The structure of the dispensing valve facilitates cleaning in situ. To this end, the dispensing valve includes a piston and a seat for the piston in the door in the product outlet, and a rolling diaphragm carried by the piston seals the receptacle from product whether the piston is either in a position to dispense product or is sealing the product outlet. In this manner, as the dispensing valve is open for dispensing the softserve product from the refrigeration machine, the diaphragm connected to the head end rolls with the upward movement of the piston leaving no cracks or crevices for the retention of unwanted products. Additionally, the openings allow for cleaning in situ of both the passageway and the dispensing outlet from the door, facilitating the maintenance of cleanliness of the machine.
Another advantage of this kind of dispensing valve for the softserve product is that a rolling diaphragm valve neither requires lubrication to keep it active nor periodic disassembly to lubricate. Moreover, by providing a novel flush system, such hard to get parts and places, such as the drive attachment to the beater, may be cleaned in situ.
The overall machine structure also provides numerous advantages. For example, the present softserve machine provides the advantages of a closed refrigeration system having a recirculating refrigerant path, the system including the conventional condenser having a liquid refrigerant output, a throttling expansion valve for changing the state of the refrigerant to a gas, and an evaporator serially connected in the refrigerant path. A subcooler is placed intermediate the condenser and the throttling expansion valve, the subcooler having a primary and secondary side. The primary side of the subcooler is in the path of the high-pressure liquid refrigerant from the condenser, and a path of gaseous refrigerant is supplied from the outlet of the evaporator to the secondary side of the subcooler, in heat exchange relation with the primary side. A heat sink in the subcooler is placed in heat exchange relation with both the primary and secondary sides of the subcooler. A tap on the liquid side of the refrigeration path, from the subcooler, forms a secondary refrigeration path for cooling a product mix container with a refrigeration coil therein so as to maintain the product mix at a predetermined temperature. The heat sink in the subcooler increases the efficiency of the system, reducing cycling of the refrigeration system, while having the ability to transfer heat out of the subcooler when the system is running and absorb heat so as to reduce the running cycle of the refrigeration system when the system is idle. This permits lengthening times or periods of passive cooling and advantageously eliminates the requirement of a separate active refrigeration system for the product mix cabinet.
Another advantage of the present softserve machine is the ability to consistently provide a predetermined mixture of product mix and a gaseous medium (e.g., air) to a freezing chamber of a softserve product refrigeration machine. This is accomplished by providing a pressurized mix container that is connected to a source of pressurized gas (e.g. air) connected to the gas or air supply inlet of the pressurized mix container. A product mix outlet from the pressurized container, in the form of a conduit, connects the pressurized mix container to the freezing cylinder of the softserve product refrigeration machine. The pressurized gaseous matter, at the same pressure as applied to the mix container, is also applied to a gaseous matter (air) injection point in the conduit to affect mixing of gas (air) and product mix before entry of the mix into the freezing chamber. By introducing a pressure adjuster (e.g., a needle valve) in the line, the ratio of gas (air) to mix may be closely regulated so as to control xe2x80x9coverrun.xe2x80x9d
Still another advantage of the present apparatus in a softserve machine is the ability to determine the amount of mix left in the pressurized mix container. This is accomplished by including a gas/air pressure dump valve intermediate the source of pressurized gas/air and the gas/air supply inlet of the mix container. The dump valve is controlled to isolate the source of pressurized gas/air from the mix container and allows the dumping of gas/air from the mix container for predetermined periods of time. The change of pressure per predetermined time of the gas/air dump indicates the quantity of mix left in the mix cabinet.
Another advantage of the apparatus of the present structure is that a simple instrument may be provided to determine when the mix is entirely gone from the pressurized mix container. To this end, an instrument, such as a thermal probe having a thermister or the like therein, may be placed at the injection point at the conduit. This means the probe is preferably placed in the mix line feeding the air/mix chamber or barrel. By forcing a small electric current through the thermister probe, as the thermister has an impedance, the current creates heating of the thermister. When mix is present, the liquid mix rapidly dissipates the heat of the thermister. But when all the mix is depleted, the thermal conductivity surrounding the probe is reduced and the thermister becomes warmer. This rise in temperature can be electrically sensed by the controls as the resistance of the thermister diminishes with rising temperature. In this manner, the control detects the presence or absence of a liquid mix.
Another distinct advantage of the apparatus of the softserve machine is a new beater assembly design (commonly called a dasher in the softserve product refrigeration machine art). The advantages of high-strength and ease of construction while maintaining better blending and consistency of product as well as increased throughput all lend themselves to a more efficient machine for dispensing softserve product. To this end, the beater assembly comprises a foraminous tube without any welded parts. The front helical portion of the beater, which forces product out of the freezer through the dispensing valve (product pushing helical member), is preferably made of an easily cleaned plastic which is readily molded and inserted, as by key ways, into one end of the foraminous cylinder. The scraping elements of the dasher or beater are also preferably composed of a material, such as a plastic, for whisking or scraping the interior surface of the freezing cylinder. These scraping elements may be provided with a snap type fitting which allows them to be snapped into place in appropriate places on the cylinder. Preferably, the scraping elements should be biased toward the interior of the freezing cylinder to compensate for wear of the scraping elements due to rotation within the freezing cylinder. The driving portion of the foraminous cylinder includes a baffle rod for non-driving engagement at one end with a rotatable drive shaft (for effecting rotation of the foraminous cylinder) and at the forward end with the door assembly or other means to inhibit rotation of the baffle rod. The baffle rod is positioned within the cylindrical beater (foraminous cylinder), and is eccentric to the centerline of the beater, and mounted so as to be stationary with respect to beater rotation. The baffle rod may include foraminous hubs or elements through which mix is forced, helping to insure a good blending of the mix in the freezing cylinder.
Still another feature of the present machine is the provision of a control for the machine which facilitates hands-off operation and adjusts the machine, regardless of the draw-down of the product, to insure the quality of the product.